1. Field of the Invention
The invention relates to a method for the treatment of incineration residues.
2. Introduction to the Invention
It is known that residues from the incineration of waste, in particular of domestic waste and waste comparable thereto, are usable as foundation material and embankment material in road construction and as gravel substitute in concrete (C.R.O.W. (1988): Residues are (no longer) waste--WIP slags. Publication 15, Stichting C.R.O.W., Ede 1!; Leenders, P. (1984): Management of Solid Waste Incinerator Residues in The Netherlands. In: K. J. Thome-Kozniensky (ed.): Recycling International, Vol. 2, p. 1420-1441. EF-Verlag, Berlin 2!).
Such residues often referred to a WIP slags, must fulfil certain civil-engineering and environmental-hygiene quality requirements, depending on the field of application. The environmental-hygiene quality requirements can be subdivided into requirements relating to the composition and requirements relating to the leachability of the product. As far as the territory of the Netherlands is concerned, these environmental-hygiene quality requirements relating to the leachability of the product. As far as the territory of the Netherlands is concerned, these environmental-hygiene quality requirements will be laid down in the so-called Building Materials Order, a General Order in Council (AMVB) within the framework of the Soil Protection Act. In said AMVB, a draft of which has been published, the stress is placed on the quality requirements relating to leaching. Of the civil engineering quality requirements which are imposed on applications as foundation material the requirements relating to unincinerated and digestible material are particularly important. For applications as gravel substitute in concrete, the pH is also important.
In order to meet the requirements of the Building Materials Order, it is often necessary to suppress the leaching of heavy metals from WIP slags. Such processes, generally referred to as immobilization processes, are generally known and are subdivided into physico-chemical and thermal processes. The object of physico-chemical processes is to produce a hard, low-porosity and durable matrix by using binders and other aggregates and at the same time fix impurities in the form of sparingly soluble compounds.
The formation of a hard matrix according to known methods, in which, for example, use is made of a binder is in general not a problem. According to leaching tests, however, in many cases no chemical binding of impurities occurs. After reduction of the matrix, the leaching is often again at the level of the starting material. Another weak point of the present physico-chemical immobilization processes is the use of relatively large amounts (typically 10-50% on a weight basis) of expensive aggregates such as cement.
The object of thermal processes is to incorporated impurities in a silicate matrix by means of sintering or melting of the material. From tests it is found that the impurities are often fixed well. A disadvantage of the process is that the costs are high as a consequence of the high investment and the considerable energy consumption.